Add accessible names to buttons in the Uber tray

ash/system/bluetooth/tray_bluetooth.cc

Index: ash/system/bluetooth/tray_bluetooth.cc
diff --git a/ash/system/bluetooth/tray_bluetooth.cc b/ash/system/bluetooth/tray_bluetooth.cc
index 43b707f9f11ad013c2957dfc1488e96737902577..3b086651fde78b5116bd7ad7d3bce17547afea5f 100644
--- a/ash/system/bluetooth/tray_bluetooth.cc
+++ b/ash/system/bluetooth/tray_bluetooth.cc
@@ -99,7 +99,8 @@ class BluetoothDetailedView : public TrayDetailsView,
         IDR_AURA_UBER_TRAY_BLUETOOTH_ENABLED,
         IDR_AURA_UBER_TRAY_BLUETOOTH_DISABLED,
         IDR_AURA_UBER_TRAY_BLUETOOTH_ENABLED_HOVER,
-        IDR_AURA_UBER_TRAY_BLUETOOTH_DISABLED_HOVER);
+        IDR_AURA_UBER_TRAY_BLUETOOTH_DISABLED_HOVER,
+        IDS_ASH_STATUS_TRAY_BLUETOOTH);
     toggle_bluetooth_->SetToggled(!delegate->GetBluetoothEnabled());
     footer()->AddButton(toggle_bluetooth_);
   }